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Abstract

An aluminum alloy member resistant to cracking and having high strengths and excellent stress corrosion cracking resistance is manufactured by expanding a 7xxx aluminum alloy hollow extrusion at a rate of 5% or more. Specifically, a 7xxx aluminum alloy hollow extrusion containing Zn of 3.0-9.5%, Mg of 0.4-2.5%, Cu of 0.05-2.0%, and Ti of 0.005-0.2%, in mass percent, and prepared through press quenching is subjected to a reversion treatment, to pipe expansion within 72 hours after the reversion treatment, and to temper aging. The reversion treatment includes heating at a temperature rise rate of 0.4° C./second or more, holding in a temperature range of 200-550° C. for longer than 0 second, and cooling at a rate of 0.5° C./second or more. The ratio Y (σ_rs/σ_0.2) of the tensile residual stress σ_rs to the 0.2% yield stress σ_0.2 after temper aging and the total content X of Mg and Zn satisfy Expression (1):

description='In-line Formulae' end='lead'Y≦−0.1X+1.4   (1).description='In-line Formulae' end='tail'

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